1. Field of the Invention
The present invention relates in general to a method and apparatus for recording an information signal on a magnetic medium and, more particularly, to a method and apparatus for recording an information signal on a magnetic tape using one or more rotary heads.
2. Description of the Prior Art
It has become standard practice in a video recorder to record an information signal on a magnetic tape by means of a rotary head as a series of parallel tracks that are obliquely arranged in relation to the direction of travel of the tape. It is also known that in order to record properly the signal in these slanted tracks the recording signal must have a predetermined phase relationship relative to the rotational phase of the rotary head. Otherwise, signals might be supplied on the recording head when it was not in contact with the tape and dropouts would occur. Typically, a separate reference signal must be provided to indicate the rotational phase of the rotary head.
In U.S. patent application Ser. No. 06/485,065, filed Apr. 4, 1983, commonly assigned herewith, it has been proposed that when a pulse-code-modulated (PCM) signal is to be recorded, the rotary head is controlled so that it comes into contact with the tape during the exact time that the PCM signal is read out of a memory. To accomplish this synchronized recording operation, the timing control of the rotary head is carried out by taking a signal representative of the rotational phase of the rotary head as a reference. One way of obtaining an appropriate reference signal indicating the rotational phase of the rotary head is to employ a pulsed signal PG, which is obtained from a pulse generator formed by a combination of a magnet and a detecting coil, with both of these elements being located within the rotary head drum. This system adequately provides the necessary reference signal having head-position pulses therein. However, the pulse generator apparatus must be disposed within the circumference of the rotary head drum. This becomes a problem when it is desired to reduce the diameter of the drum in order to reduce the size of the overall rotary head and tape-guide drum assembly, for example, when embodying the apparatus as a portable video camera. Thus, the space required for the pulse generator becomes a limiting factor because the diameter of the rotary head drum can not be reduced, since space must be left to mount the magnet and detecting coil therewithin.
Not only does this pulse generator structure place a limitation on the minimum diameter of the tape-guide drum but its requirement adds to the construction costs and complexity of the entire rotary head drum assembly. Moreover, the accuracy with which these pulses must be generated requires critical adjustments between the head mounting position and the mounting position of the pulse generator and, thus, such adjustments become both troublesome and time consuming.